The present invention addresses the problem of providing a new artificial nucleic acid, a production method therefor, and a use thereof. The problem can be solved by an artificial nucleic acid having a unit derived from a compound represented by formula (1) or a salt thereof (in the formula, Base represents an aromatic heterocyclic ring group optionally having a substituent or an aromatic hydrocarbon ring group optionally having a substituent, A1 represents a straight-chain alkylene group, A2 represents a single bond or an alkylene group, X represents an alkylene group optionally having a substituent, R1 and R2 are the same or different from each other and each represent a hydrogen atom, an alkyl group optionally having a substituent, an alkenyl group optionally having a substituent, a cycloalkyl group optionally having a substituent, a cycloalkenyl group optionally having a substituent, an aryl group optionally having a substituent, a protecting group of a hydroxyl group, a phosphino group having a substituent, a dihydroxyphosphinyl group optionally having a substituent, or a hydroxymercaptophosphinyl group optionally having a substituent, or R1 and R2, together with two oxygen atoms respectively adjacent thereto and carbon atoms at positions 3-5 of a furanose, form a ring optionally having a substituent, and R3 represents an amino group optionally having a substituent).La présente invention traite le problème de la fourniture d'un nouvel acide nucléique artificiel, son procédé de production, et une utilisation associée. Le problème peut être résolu par un acide nucléique artificiel ayant un motif dérivé d'un composé représenté par la formule (1) ou d'un sel de celui-ci (dans la formule, la base représente un groupe cyclique hétérocyclique aromatique ayant facultativement un substituant ou un groupe cyclique hydrocarboné aromatique ayant facultativement un substituant, A1 représente un groupe alkylène à chaîne droite, A2 représente une liaison simple ou un groupe a
